The main area code, 306, is one of the original 86 area codes assigned in 1947, in the contiguous United States and the then-nine-province extent of Canada. Saskatchewan's second area code, 639,[1][2][3] was introduced in 2012, and is an overlay of 306.[4]

Despite Saskatchewan's small population, 306 was on the verge of exhaustion due to Canada's inefficient number allocation system. All competitive local exchange carriers are allocated exclusive access to at least one three-digit prefix – comprising 10,000 numbers each – for every rate centre where they plan to offer service, even for the smallest hamlets. While each competing carrier did not necessarily need that many numbers in a particular market, unused numbers were not available for use elsewhere once they were assigned to a particular carrier and rate centre. Since number pooling is not used as a relief measure in Canada, this resulted in thousands of wasted numbers. The number shortage was exacerbated by the proliferation of cell phones and other mobile devices requiring unique telephone numbers, particularly in Regina and Saskatoon.

Unlike what was previously done in jurisdictions such as neighbouring Alberta, It was decided to implement the new area code as an overlay rather than a split. Overlays have become the preferred method of area code relief in Canada; no area codes have been split in the country since 1999. SaskTel and other carriers pushed for an overlay because they did not want to force existing subscribers, particularly in rural areas, to change their numbers. 10-digit-dialing began in 2012, and became mandatory throughout the province in May 2013. Until the implementation of 639, Saskatchewan was the last of Canada's original NPAs where seven-digit dialling had not been broken.